Network Working Group YL. Zhao Internet-Draft J. Zhang Intended status: Informational TT. Peng Expires: April 26, 2012 XS. Yu BUPT XP. Cao DJ. Wang ZTE Corporation October 24, 2011 PCEP Protocol Extension for spectrum utilization optimization in Flexi- Grid Networks draft-zhaoyl-pce-flexi-grid-pcep-ex-00 Abstract Flexi-grid networks overcomes the fixed grid channel of Wavelength Switched Optical Network(WSON) by flexible spectrum to allow non- uniform and dynamic allocation of spectrum based on the demand of the incoming services' LSP. Flexi-grid networks is an effective solution to solve the problem of efficient spectrum utilization. Because the client LSP needs to be assigned contiguous spectrum in flexi-grid networks, there will be two problems that would affect spectrum utilization, i.e. RSA and fragmentation. We introduce two kinds of methods which can improve the spectrum utilization further, and some related PCEP extensions are defined in this document. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 26, 2012. Copyright Notice Zhao, et al. Expires April 26, 2012 [Page 1] Internet-Draft PCEP Extension October 2011 Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 3. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 4. RSA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Introduction of RSA . . . . . . . . . . . . . . . . . . . 4 4.2. Algorithms of RSA . . . . . . . . . . . . . . . . . . . . 4 4.3. RSA Schemes Selection . . . . . . . . . . . . . . . . . . 5 5. Defragmentation . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Motivation of Defragmentation . . . . . . . . . . . . . . 6 5.2. Definition of Defragmentation . . . . . . . . . . . . . . 6 5.3. Application Scene of Defragmentation . . . . . . . . . . . 6 6. PCEP Protocol Extension . . . . . . . . . . . . . . . . . . . 7 6.1. PCEP Protocol Extension for RSA . . . . . . . . . . . . . 7 6.2. PCEP Protocol Extension for Defragmentation . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. Normative References . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Zhao, et al. Expires April 26, 2012 [Page 2] Internet-Draft PCEP Extension October 2011 1. Introduction Demand of traffic is increasing exponentially and already approaching the limit of single mode fiber capacity. At the same time, because of varying demand of traffic, we need an efficient and agile utilization of the optical spectrum. ITU-T Study Group 15 introduce a new flexi-grid networks to enable dynamic allocation of spectrum resource. The flexi-grid networks is an effective solution to solve the problem of efficient spectrum resource utilization. The granularity of flexi-grid networks can be smaller and agile. i.e.,6.25GHz. In the flexi-grid networks, the appropriate size of spectrum is determined by the used modulation format.According to the client data rate LSP and physical consecutives of the selected path,the appropriate size of spectrum is adaptively allocated to optical connections by assigning the appropriate number of contiguous spectrum from end-to-end.Before assigning the client LSP, we have to find suitable route and fit contiguous spectrum for it, and it is a complex process. So spectrum utilization is very important in RSA. While there are several algorithms for RSA, flexi-grid networks require to extend PCEP protocol to support different algorithms seletion. Upon tearing down of connections, the allocated spectrum are released for future LSPs. In a dynamic traffic scenario, this setup and tear down precedure for a channel leads to fragmentation of spectral resources. Due to the fragmentation, the available spectrum is divided into small noncontiguous spectral bands,the spectral effciency in the network is compromised. Therefore the probability of finding suffcient contiguous spectrum for a connection is decreased. We introduce defragmentation to deal with fragmentation in flexi-grid networks. then PCEP protocol has to add some messages to support them. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Terminologies RSA: Routing and Spectrum Assignment Zhao, et al. Expires April 26, 2012 [Page 3] Internet-Draft PCEP Extension October 2011 WSON:Wavelength Switched Optical Network 4. RSA 4.1. Introduction of RSA In this part, we focus on the routing and spectrum assignment (RSA) problem. This problem can be partitioned into two subproblems: (1) routing and (2) spectrum assignment, and each subproblem can be solved separately. Different from traditional WDM network, flexi- grid networks assign continuous spectrum for new arrival LSP. Static planning models are used for flexi-grid networks to improve spectrum utilization. 4.2. Algorithms of RSA There are several spectrum assignment algorithms. (1)Random Fit (RF) This scheme first searches the space of spectrum to determine the set of all spectrum that are available on the required route. Among the available spectrum, one is chosen randomly. (2)First-Fit (FF) In this scheme, all spectrum is numbered.When searching for available spectrum, a lower numbered spectrum is considered before a higher- numbered spectrum.The first available spectrum is then selected. Compared to Random spectrum assignment, the computation cost of this scheme is lower because there is no need to search the entire spectrum space for each route. (3)Least-Used (LU)/SPREAD LU selects the spectrum that is the least used in the network, thereby attempting to balance the load among all the spectrum. The performance of LU is worse than Random, while also introducing additional communication overhead (e.g., global information is required to compute the least-used spectrum). (4)Most-Used (MU)/PACK MU is the opposite of LU in that it attempts to select the most-used spectrum in the network. The communication overhead, storage, and computation cost are all similar to those in LU.MU also slightly outperforms FF, doing a better job of packing connections into fewer Zhao, et al. Expires April 26, 2012 [Page 4] Internet-Draft PCEP Extension October 2011 spectrum and conserving the spare capacity of less-used spectrum. (5)Min-Product (MP) MU is the opposite of LU works. In a single fiber network, MP becomes FF. The goal of MP is to pack spectrum into fibers, thereby minimizing the number of fibers in the network. (6)Least-Loaded (LL) The LL heuristic, like MP, is also designed for multi-fiber networks. This heuristic selects the spectrum that has the largest residual capacity on the most loaded link along route. (7)MAX-SUM (MS) MS was proposed for multi-fiber networks but it can also be applied to the single-fiber case.MS considers all possible paths in the network and attempts to maximize the remaining path capacities after lightpath establishment. (8)Relative Capacity Loss (RCL) RCL is based on MS. RCL chooses spectrum to minimize the relative capacity loss. RCL is based on the observation that minimizing total capacity loss sometimes does not lead to the best choice of spectrum. (9)Spectrum Reservation (Rsv) In Rsv, a given spectrum on a specified link is reserved for a traffic stream, usually a multihop stream. This scheme reduces the blocking for multihop traffic,while increasing the blocking for connections that traverse only one fiber link (single-hop traffic). (10)Protecting Threshold (Thr) In Thr, a single-hop connection is assigned spectrum only if the number of idle spectrum on the link is at or above a given threshold. 4.3. RSA Schemes Selection There are several spectrum assignment algorithms, we have to choose one of them for flexi-grid networks. Different RSA schemes are selected according to diffrent network condition. The PCEP protocol needs to extend a bit that shows different schemes selected. Zhao, et al. Expires April 26, 2012 [Page 5] Internet-Draft PCEP Extension October 2011 5. Defragmentation 5.1. Motivation of Defragmentation New arrival of LSPs are then either forced to utilize more spectrum in the network or blocked in spite of suffcient spectrum being available. Additionally, as the network evolves, a current optimal routing scheme might no longer provide the optimal spectral utilization over time. There is an increasing demand from the network operators to be able to periodically reconfigure the network and return it to its optimal state, so that the network can operate more effciently. 5.2. Definition of Defragmentation There is an operation defined as network defragmentation to solve above problem. Reducing the blocking by consolidating the available network resources, this operation will also enable better network maintenance and more effcient network restoration and bandwidth adjustment. 5.3. Application Scene of Defragmentation The process of defragmentation: (1) select LSP for defragmentation, and interrupt it considerring the time and cost, (2) choose forward spectrum in original route or new route, (3) move the LSP on possible spectrum. An example of defragentation is as following: A,B,C are client LSPs on link l, l1 is original statement of link l,l2 is statement of link l after defragementation. +-------------+ +----+ +---------+ l1: | A | | B | | C | +-------------+----------+----+-----+---------+-- +-------------+----+-----------+ l2: | A | B | C | +-------------+----+-----------+----- Fig.1 Defragentation principle we first focus on the problem of the time-point when should defragmentation be operated. There is two ways to solve this problem. One way is new arrival LSPs have no sufficient spectrum to bear, then cause blocked in the network. The other way: (1) collect Zhao, et al. Expires April 26, 2012 [Page 6] Internet-Draft PCEP Extension October 2011 the information about occupation of spectrum fragments in a link or in the network, (2) introduce a notation to describe the state of spectrum fragment in a link or in a network, (3)when the size of this notation reaches an assumed threshold, it is the time for defragmentation. we consider the methods of defragmentation. At present, there is two methods for defragmentation. First is change route of client LSP, meaning that the spectrum of this LSP in new route is ahead than the spectrum in original route. Second is the LSP move forward directly in original route. 6. PCEP Protocol Extension 6.1. PCEP Protocol Extension for RSA The PCEP protocol need to be extended to support the algorithms choosing of RSA. PCReq needs to add RAEO-list information. This information include "Algorithm Id", which stands for the number of different algorithms, and "Pri" that means priority of these algorithms. ::= [] [] [] [] [[]] [] [] where RP Object: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |C|O|B|R| Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Request-ID-number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | Zhao, et al. Expires April 26, 2012 [Page 7] Internet-Draft PCEP Extension October 2011 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ C bit is the Cascade bit, if C=1,assign continuous spectrum for traffic else assign uncontinuous spectrum. [] defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Object-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Algorithm Id | Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ::= [] [] [] NO-PATH: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Nature of Issue|C| Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: NO-PATH Object Format NI - Nature of Issue (8 bits): The NI field is used to report the nature of the issue that leads to a negative reply. Two values are currently defined: 0: No path satisfying the set of constraints could be found 1: PCE chain broken 2: No path satisfying the Continuous spectrum Zhao, et al. Expires April 26, 2012 [Page 8] Internet-Draft PCEP Extension October 2011 6.2. PCEP Protocol Extension for Defragmentation The presence of defragmentation in flexi-grid networks has an impact on the information that needs to be transferred by the control plane and PCE. Defragmentation has to interrupt the traffic and move it to another spectrum or route. The PCEP protocol needs to be extended two messages to support defragmentation, ingcluding information of orginal route/spectrum and present route/spectrum, when to stop defragmentation and so on. Here is Spectrum Defragmentation Request Message and Spectrum Defragmentation Reply Message. "Target Clutter Value" stands for the goal of defragmentation. "R" means whether the network MUST make it. Spectrum Defragmentation Request Message ::= [LSPA Object] [] Spectrum Defragmentation Reply Message ::= [LSPA Object] [] Spectrum Defragmentation Reply Message SDTO: Spectrum Defragmentation Target Object Zhao, et al. Expires April 26, 2012 [Page 9] Internet-Draft PCEP Extension October 2011 SDTO:Spectrum Defragmentation Target Object 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Object-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |R| Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Target Clutter Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ::=
where Center Frequence is 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Center Frequence | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Center Frequence (32 bits): The requested bandwidth is encoded in 32 bits, expressed in bytes per second. 7. Security Considerations TBD. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFC's to Indicate Requirement Levels", RFC 2119, March 1997. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. Zhao, et al. Expires April 26, 2012 [Page 10] Internet-Draft PCEP Extension October 2011 Authors' Addresses Yongli Zhao BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613811761857 Email: yonglizhao@bupt.edu.cn URI: http://www.bupt.edu.cn/ Jie Zhang BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613911060930 Email: lgr24@bupt.edu.cn URI: http://www.bupt.edu.cn/ Tiantian Peng BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8615116984347 Email: tt871228@163.com URI: http://www.bupt.edu.cn/ Xiaosong Yu BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613811731723 Email: yu.xiaosong@qq.com URI: http://www.bupt.edu.cn/ Zhao, et al. Expires April 26, 2012 [Page 11] Internet-Draft PCEP Extension October 2011 Xuping Cao ZTE Corporation No.16,Huayuan Road,Haidian District Beijing 100191 P.R.China Phone: +8615801379189 Email: cao.xuping@zte.com.cn URI: http://www.zte.com.cn/ Dajiang Wang ZTE Corporation No.16,Huayuan Road,Haidian District Beijing 100191 P.R.China Phone: +8613811795408 Email: wang.dajiang@zte.com.cn URI: http://www.zte.com.cn/ Zhao, et al. Expires April 26, 2012 [Page 12]